During summer of 1993, a novel syndrome was identified in the Four Corners area of the United States, caused by a previously unknown bunyavirus (Hanta sin nombre). While virus is found systemically in patients that died from the infection, the pulmonary pathogenesis remains to be elucidated. To that extent, 6 rhesus macaques were infected with HSNV either intranasally or iv. All animals showed no clinical symptoms and viral burdens remained low to undetectable. The animals responded however with antibody titers, low levels of IFNK and virus specific cell mediated responses. The nature and magnitude of these responses are currently being evaluated and will be compared with values obtained on human patients.